There is normally considerable activity around a loading dock for factories, warehouses and the like. Normally the transport vehicles to be loaded or unloaded with equipment and goods are parked against the dock to enable forklift trucks and the like to travel onto and off of the vehicle. Quite often dock levellers are used in conjunction with such docks to bridge the gap between the dock and the truck vehicle. There have been instances, particularly in busy dock areas, where the parked vehicle moves away from the dock, either due to driver error in not realizing that the vehicle is still being unloaded, or because a braking mechanism or the like is not in place and the vehicle simply rolls away from the dock. This can result in very hazardous conditions, for example, should the forklift operator be driving onto the truck bed or off of it and the vehicle begins to move away, the forklift truck can fall from the dock causing injury to the operator and loss of equipment and product. It is therefore important to provide a device which will engage a portion of the parked vehicle frame to ensure that it is held in place or restrained in moving away from the dock.
U.S. Pat. No. 4,191,503 discloses a hook and cable arrangement for restraining movement of the parked vehicle. The hook is attached to a suitable portion of the vehicle frame and the cable drawn in until the cable is taut thereby restraining vehicle movement away from the dock.
U.S. Pat. No. 4,443,150 discloses a hook for engaging a portion of the vehicle, such as the ICC bar at the rear of the vehicle. The hook, as it remains in its outwardly extending position, can be moved manually from a lower position to an upper position at which point it engages the ICC bar of the vehicle rear. A roller system is provided to raise and lower the guard to the desired elevation. The hook can then be raised and lowered from within the guard to either engage or disengage the ICC bar. A ratchet type mechanism holds the hook in the raised position in capturing the ICC bar of the vehicle.
There is also a variety of vehicle restraints which rely on pivotal rotation of a hook. The hook is pivoted from a depending position to an elevated position to engage a portion of the parked vehicle to restrain movement thereof away from the dock. Examples of pivotal arrangements for the various types of hook devices are disclosed in U.S. Pat. Nos. 4,208,161, 4,282,621, 4,379,354 and 4,560,315. With reference to these patents, in one manner or another the vehicle engaging hook device is pivoted from a dependent position to an elevated position to engage the ICC bar. It is appreciated that a variety of sensors may be used in combination with these devices to indicate when the hook has engaged the vehicle to restrain movement away from the dock.
U.S. Pat. No. 4,472,099 discloses another form of pivotal swinging of a hook to engage the vehicle ICC bar or the like. A ram, in combination with a pivotal lever 24, is used to swing the hook from the dependent position to the elevated vehicle engaging position. The lever, as it is pivoted by the ram, has an end portion which slides along the rear portion of the hook to cause rotation of the hook from the depending to the elevated position. U.S. Pat. No. 4,630,989 discloses the use of a hydraulic ram to pivotally swing a bar from a horizontal to vertical position. The bar, when elevated to the vertical position, captures the ICC bar portion of the vehicle to restrain movement of the vehicle away from the dock.
Problems associated with these types of systems are the lack of durability and/or ineffective capturing of a vehicle portion to restrain the vehicle against a dock.